1. Field of the Invention
The present invention relates to an information processing system using a two-dimensional data symbol.
2. Description of the Related Art
Conventionally, there is known a prepaid card system, such as a telephone card. In the prepaid card system, various information is magnetically recorded in a magnetic recording area of a card, in accordance with the operational parameter data contained in the prepaid card, and the information in the magnetic recording area is read by a card reader when the card is used, by which the operational parameter data of the card is determined and, if necessary, revised. If the operational parameter data exceeds the operational parameters of the card, namely, the card has reached "0" units, the card becomes redundant.
However, since it is a simple process to magnetically record information in the magnetic recording area, the data contained in the magnetic recording area can be easily counterfeited, enabling the previously redundant card to be reused illegally.